Inhibition of human gastric adenocarcinoma xenograft growth in nude mice by α-difluoromethylornithine

We studied the effect of inhibition of polyamine biosynthesis by a-difluoromethyloniithine on the growth of a human gastric adenocarcinoma (CLEES) xenotransplanted in nude mice. CLEES is a well-differ-entiated gastric adenocarcinoma of the intestinal type. The doubling time has ranged from 7 to 10 days through 11 passages. Electron microscopic and immunohistochemical studies comparing the original tumor and xenotransplants showed similar structure and similar amounts of card-noembryonk antigen. Polyamine biosynthesis is required for cell division. cr-Difluoromethylornithine inhibits ornithine decarboxylase, the rate-limiting enzyme in polyamine biosynthesis. In this study, 48 athymk mice were used in two experiments. In the first experiment, two groups of 12 mice each were inoculated with CLEES tumor cells and received either tap water or a 3% α-difluoromethytornithine solution as drinking water. Tumor size was measured twice weekly. Tumor size was significantly decreased from controls by the fourth week of treatment and at all points of analysis thereafter for 7 wk. In the second experiment a-difluoromethykHnithine significantly reduced tumor concentrations of the polyamines putresdne and spermidine. In addition, the tumor content of DNA was significantly reduced in treated mice (0414 ± 0.16 mg) compared to controls (4.76 ± 0312 mg). Our data suggest that inhibition of polyamine biosynthesis may be a useful component of multidrug chemotherapy for human gastric adenocarcinoma. Establishment of tumor lines such as this gastric adenocarcinoma will facilitate further studies on the biological behavior of human gastric cancer and its response to chemotherapeutic manipulation in vivo.